1. Field of the Invention
The present invention generally relates to an exchange and, more particularly, to an exchange which changes a route of a transmission path, when a malfunction occurs in one of a plurality of switches, so as to bypass the malfunctioning switch.
In an exchange or a transmission apparatus which communicates information including audio data and image data, a switch network is provided with a plurality of inputs and outputs so that any one of the inputs can be connected to any one of the outputs so as to arbitrarily change a route of a communication path formed in the switch network.
2. Description of the Related Art
A description will now be given of a conventional method for avoiding influence of a malfunction occurring in one of a plurality of switches which constitute a switch network in an exchange.
FIGS. 1, 2 and 3 show a first, second and third conventional exchange, respectively.
The first conventional exchange shown in FIG. 1 comprises a working switch network 101, a spare switch network 102 having the same structure as the working switch network 101, an input switching unit 103 and an output switching unit 104. The working switch network 101 comprises a plurality of switches, and has a plurality of inputs and a plurality of outputs. The input switching unit 103 and the output switching unit 104 change a transmission path formed through the exchange so that the transmission path is formed in the spare switch network 102 instead of the working switch network 101 when a malfunction occurs in one of the switches in the working switch network 101 which is actually being used.
When a malfunction occurs in one of the switches constituting the working switch network 101, the first conventional exchange bypasses the malfunctioning switch by switching the actually used switch network from the working switch network 101 to the spare switch network 102. This switching operation is performed by the input switching unit 103 and the output switching unit 104. Transmission paths formed after the switching operation are also formed in the spare switch network 102.
The second conventional exchange shown in FIG. 2 comprises a switch network 111, an input switching unit 112, an output switching unit 113 and a header changing table circuit 114. The switch network 111 comprises a plurality of switches and a plurality of spare switches reserved for spare use. The switch network 111 has a plurality of inputs and a plurality of outputs, and also has a plurality of spare inputs and a plurality of spare outputs. The input switching unit 112 and the output switching unit 113 change a route of a transmission path formed through the exchange so that the transmission path is formed between one of the spare inputs and one of the spare outputs when a malfunction occurs in one of the switches included in the transmission path in the switch network. The header changing table circuit 114 changes input address information, which is included in communication information to be transmitted, to input address information of one of the spare inputs.
When a malfunction occurs in one of the switches in the switch network 111, the second conventional exchange bypasses the malfunctioning switch by changing a route of the transmission path including the malfunctioning switch to a route formed between one of the spare switches and one of the spare inputs.
The third conventional exchange shown in FIG. 3 comprises a switch network 121 including a plurality of switches. The switch network 121 has a plurality of inputs and a plurality of outputs. When a malfunction occurs in one of the switches constituting the switch network 121, the malfunctioning switch is detected so that a transmission path routing the malfunctioning switch is changed to a transmission path routing a spare switch instead of the malfunctioning switch.
However, each of the above-mentioned conventional exchanges has the following problems.
In the first conventional exchange, since a detection of the malfunctioning switch in the actually used working switch network 101 is not performed, a transmission path routing the malfunctioning switch cannot be distinguished. Thus, all transmission paths including normal transmission paths must be switched to transmission paths formed in the spare switch network 102 when a malfunction occurs in one of the switches in the working switch network 101.
In the first, second and third conventional exchanges, since the spare switch network or the spare switch must be reserved for spare use which is not used in a normal condition, weight and size of the entire system is increased and also manufacturing cost of the exchange is increased.
It is a general object of the present invention to provide an exchange in which the above-mentioned problems are eliminated.
A more specific object of the present invention is to provide an exchange in which, when a malfunction occurs in one of a plurality of switches, a transmission path bypassing the malfunctioning switch can be formed in the absence of a spare switch in the exchange so as to decrease weight and size of the entire system.
In order to achieve the above-mentioned objects, there is provided according to the present invention an exchange setting a transmission path for transmitting communication information through a switch network comprising a plurality of switches, the switch network provided with a plurality of inputs and a plurality of outputs so that the transmission path is formed between one of the inputs and one of the outputs by routing the switches in the switch network, the exchange changing a route of the transmission path when a malfunction occurs in one of the switches included in the transmission path so as to bypass the malfunctioning switch, the exchange comprising:
a malfunctioning switch detecting unit detecting a location of the malfunctioning switch in the switch network; and
changing means for changing the route of the transmission path by switching one of the inputs and outputs connected to the transmission path based on predetermined routing information so as to bypass the malfunctioning switch.
According to the above-mentioned invention, when a malfunction occurs in one of the switches constituting the switch network, the location of the malfunctioning switch is detected and the location information is supplied to the changing means. The location information may include an address of the malfunctioning switch and information indicating a position of the malfunctioning switch with respect to the inputs and outputs of the switch network. For example, if the switches in the switch network are arranged in a matrix, the location information may include indication of a column (stage) in which the malfunctioning switch is included. When the changing means receives the location information, the changing means changes the route of the transmission path by changing one of the inputs which is connected to the transmission path or changing one of the outputs connected to the transmission path. That is, the input or the output connected to the transmission path is changed to another input or output based on the routing information which indicates a route which bypasses the malfunctioning switch. That is, the route of the transmission path can be changed to a route which bypasses the malfunctioning switch by merely changing the input or output of the switch network.
Accordingly, the exchange according to the present invention discriminate the transmission path including the malfunctioning switch, and the route of the transmission path is changed by changing the input or the output of the switch network based on the location of the malfunctioning switch. Thus, the exchange according to the present invention does not need a spare switch which is not used when the exchange is operated in a normal condition. Therefore, the weight and size of the entire system is reduced which is advantageous for reducing manufacturing cost.
In the exchange according to the present invention, the changing means may comprise:
a storing unit which stores table information indicating a plurality of routes each of which bypasses one of the switches in the switch network, each of the routes being indicated in relation to one of the inputs and outputs of the switch network; and
a selecting unit selecting one of the routes indicated in the table information so as to change the route of the transmission path to bypass the malfunctioning switch.
Accordingly, if the location of the malfunctioning switch is detected, a route which bypasses the malfunctioning switch can be obtained from the table information in relation to the input or the output of the switch network.
In one embodiment according to the present invention, the changing means may comprise:
an input switching unit switching the input of the switch network;
an output switching means switching the output of the switch network; and
input and output selecting means for selecting one of the input switching unit and the output switching unit so that the changing means changes the route of the transmission path by the selected one of the input switching unit and the output switching unit.
The input and output selecting means may select the input switching unit when the malfunctioning switch is one of the switches directly connected to the input switching unit. Additionally, the input and output selecting means may select the output switching unit when the malfunctioning switch is one of the switches directly connected to the output switching unit.
Additionally, the input and output selecting means may select the input switching unit when the malfunctioning switch is one of the switches other than the switches directly connected to one of the input switching unit and the output switching unit. Alternately, the input and output selecting means selects the output switching unit when the malfunctioning switch is one of the switches other than the switches directly connected to one of the input switching unit and the output switching unit.
Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.